RAAL Requisite CA-1a FilterSet

(7 customer reviews)

US $ 200.00

The RAAL CA-1a Neutral FilterSet package contains two complete filtersets for both earpads. Each filterset contains filters with sample rates from 44.1 kHz to 352.8 kHz and packaged as a .zip file that can be used in most convolvers, like Hang Loose Convolver and Roon for example. Mono 352.8 kHz mono filters are also included for HQPlayer.

FilterSet Free Trial Offer: Download the Hang Loose Convolver 14-Day Free Trial software. Specify the RAAL CA-1a Neutral FilterSet in the Order Notes at checkout.

Full Product Description

Frequency Response Measurement & Correction

RAAL requisite CA-1a closed frequency

Closed earpads

RAAL requisite CA-1a open frequency

Open earpads

RAAL requisite CA-1a closed phase reponse

The RAAL requisite CA-1a is a ribbon headphone. Depending on which earpad is used, produces a significantly different sonic signature. While the closed earpads produce a reasonably smooth response up to 1 kHz, there is a significant wide band -8 dB dip in frequency response from about 1.5 kHz to 5 kHz. This results in a very dark sound.

While the open earpads aren’t as dark sounding, there is a lack of deep bass response with a 1.2 kHz peak and then another -6dB dip in frequency response between 1.5 and 3.5 kHz, right where out ears are the most sensitive. The rising narrow band peak at 5 kHz gives the headphone the impression of being a bit brighter than the closed earpads, but still very midrange-y sounding.

With the addition of the phase response chart, the CA-1a have phase issues that obfuscate the clarity and depth of field that these headphones are capable of.

Engaging the high-resolution convolution filter is indeed a “night and day” difference in sonic signature of these headphones. With the convolution filter engaged, using either set of earpads, the response is ruler flat from 15 Hz to 5 kHz +- 0.5 dB. The convolution filters fully optimize the ribbon design and manufacture of these headphones.

7 reviews for RAAL Requisite CA-1a FilterSet

  1. Majuto (verified owner)


    HLC and Raal CA-1a neutral filter sets are my first true encounter with music listening and digital sound manipulation in home listening.

    When writing this short review I’ve listened Raals for about a week. First evening Raals as pure and after that with HLC and filters within a trial period. Now I’ve bought them.
    I’ve listened them with the basic cable and good but not near TOTL amps or dac.

    Raals as pure sound imo really interesting, a bit wild and with a difficultly definiable sound quality, which in longer listening sessions might turn into slight fatigue.

    Then HLC and filters on. Could I describe it to sonic wonder, maybe but anyhow the change in sound is really remarkable. The sound especially with open pads is very balanced, detailed and musical. With my amps the bass could be perhaps a bit more elevated. This might on the other hand be consequence of getting used to Harman target type frequency curve listening norm.

    My getting use to Raal sound period isn’t ready yet. I would anyhow like to say that with HLC and neutral filters (and with my equipment) Raal is clearly a more generally competent and a truly
    great headphone. It’s pure properties make it unique in a sense, but HLC and filtersets make it a most propriate headphone for everyday use and long listening sessions. So I can truly recommend Accurate Sounds DSP achievements although I earlier was quite sceptic towards EQing and sound manipulation.

  2. raidrus

    These filters are essential for this headphone. They go from having wonky tonality to becoming neutral enough to mix and master on. Plus, I believe they are reducing distortion or maybe it’s the corrected phase issues, but something really amazing is going on with them on the CA-1a that once you hear, you can’t go back to unfiltered.

  3. TB (verified owner)

    Adding this filter set to Audirvana, the RAAL CA-1a headphones went from amazing to “off the charts”!

    Immediately, there were sonic improvements across the board. Bass was cleaner, faster, and had more impact. Mids gained clarity and a bit of richness and weight. The highs were cleaner as well.

    Overall, the balance improved across the spectrum.

    I was surprised that the PRAT (Pace, Rhythm and Timing) improved as much as it did.

    For $200, this has to be the biggest audio bang-for-the-buck I’ve experienced in my “audio journey”.

    Mitch has created outstanding filters, and everyone should experience the joy they provide.

  4. nfandi (verified owner)

    I was quite happy listening to my music with the CA1a before I tried the filters but now I couldn’t go back to that. The phones already had great transient response and detail but now the word that comes to mind is “balance”. The bass is more extended, but very clean and clear; no boom and bloom. Nothing stands out; nothing dominates; it’s all just very clean and clear and enjoyable to listen to. I think the CA1a + convolution filter has to be one of the best vfm TOTL combinations available today.

  5. Igor Petruk (verified owner)

    With open (coffee bean) pads these filters were not improving the sound strictly speaking. It made the sound different. More neutral, as they claim, but subjectively the music became more detailed, and less fun, enganging. To me none of those was strictly better, but different.

    Where these filters really shine to me is with closed pads. The difference is very big. The sound now is just perfect, the filters fixed the looseness of bass. You can hear more texture of the said bass across the whole low frequency range. With the filters they sound both better than open pads (with or without filters) and probably better or equal than any headphones I have ever heard.

  6. GM (verified owner)

    Excellent filter, a must have for the CA-1a. I recently heard the new $6k STAX X9000 and honestly this headset is comparable to that with these filters. You get the air of an electrostat and the bass of a planar, these ribbon headphones are special, especially with this filter.

  7. Bard Geesaman (verified owner)

    Headphones were dreadful before applying these filters. Now sound as good as any I have listened to. I was amazed to hear now much soundstage and imaging improved.

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